Printed circuit board component conveyor apparatus and process

ABSTRACT

A printed circuit board conveyor apparatus has a conveyor for moving a planar circuit board components mounted on frames, in a vertical plane, seriatim, along a first path through a spray treatment area. The components are then raised and returned toward a starting point along a second path with additional processing occurring during the return trip. The use of an overhead return along with positive positioning of the components provides substantial efficiency and allows precision and accuracy in treatment of printed circuit board components while minimizing floor space requirements.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.455,956 filed Jan. 6, 1983 now U.S. Pat. No. 4,454,003.

BACKGROUND OF THE INVENTION

Printed circuit boards have come into increasing use in the electronicsindustry. Particularly with miniaturization, the need for high speedefficient and accurate processing of printed circuit board componentshas increased. Often the circuit board components start with a basesheet of insulating material which may have bound to one or both sidesthereof a layer of copper. The base is often called a substrate and cantake the form of epoxy, glass or various polymeric materials.

The processing steps on printed circuit board components are oftencarried out in conveyor apparatus along horizontal paths where varioustreating stations expose the board components to processing. These stepscan be developing, rinsing-etching, rinsing-resist stripping-rinsing,black oxide coating, drying and the like.

Often apparatus for conveying and treating the printed circuit boardstake up substantial manufacturing area space. Lines can run from ten tothirty feet in horizontal space. Problems sometimes arise in spraytreating as in developing, etching, washing and stripping. The boards atstages of manufacture are often non-rigid and tend to wiggle whenexposed to spray baths and the like. This can lead to non-uniformity inapplication of sprayed materials. Horizontally sprayed boards tend topuddle on the upper face while the lower face also tends to havenon-uniform deposits formed thereon.

DESCRIPTION OF PREFERRED EMBODIMENTS

It is an object of this invention to provide a conveyor apparatus fortreating of printed circuit board components rapidly and efficientlywhile maintaining rigid and non-rigid sheets of components insubstantially non-distorted configuration during treatment.

Another object of this invention is to provide an apparatus inaccordance with the preceding apparatus wherein a plurality of framesare mounted on a conveyor with the frames positively held in verticalposition restraining the components against substantial lateral movementand maintaining the components at predetermined distances from sprayapparatus located on either side of the components.

Still another object of this invention is to provide an apparatus inaccordance with any of the preceding objects which provides forefficient operation with conveyance of a plurality of components towardand away from a starting point to minimize space needs in manufacture.

Still another object of this invention is to provide methods forefficiently processing printed circuit components as in the apparatus ofthis invention.

According to the invention a printed circuit board conveyor apparatushas a spray treatment line and moves a substantially planar circuitboard component along the line with the component having first andsecond sides exposed to the spray. The component along with a pluralityof seriatim arranged similar components moves along a firstsubstantially horizontal path at a first level, from a starting point toa distant point, and then back toward the starting point at a secondlevel in a second path. The apparatus has a frame means for mounting thecircuit board components for movement away from the starting point.Liquid spray and air spray means are positioned on either side of thepath at the first level for uniformly spraying the circuit board sideswith liquid to carry out a printed circuit processing step with airspray preferably between selected processes. A conveyor guide meanscontacts the frame means in supporting relationship therewith tomaintain a predetermined position of the frame and fixed position of thecircuit board component mounted thereon to aid in uniform application ofliquids by the liquid spray means. Preferably conveyor guide meansprevents movement of the circuit board component more than one inch outof vertical predetermined position. A conveyor drive means mounts theframe means for moving the circuit board in the first and second path ata first and second level respectively with the second level being abovethe first level whereby the board can be returned to the starting pointby the conveyor means. Preferably the frame means are mounted verticallyand with the plane of the printed circuit boards substantially paralleland in line with the first and second path.

According to a method of this invention, printed circuit boardcomponents are treated seriatim in a plurality of spraying stations. Theboards are mounted seriatim on a first conveyor with frame means formovement along a first path, at a first level, from a starting point toa distant point. Then upward movement moves the frame means to a secondpath returning toward said starting point at a level raised above saidfirst path. The components are fixed to a plurality of frames of theframe means by releasable means with the components held against swayfrom the vertical path by positive means at upper and lower portions ofthe components. The components are advanced along the first and secondpath so that a single operator can operate the method with a high degreeof precision with respect to spray treatments of the components at thepath with little movement of the components except in the direction ofthe path.

It is a feature of this invention that since the boards are positivelyheld in a releasable frame, even though they may be non-self-supporting,they will be substantially planar when subjected to spray by the spraymeans, thus allowing even and uniform coatings. This increases precisionand accuracy of completed printed circuit boards. Since the overheadreturn is used, space saving is maximized and a single operator can bothload and unload the frames. Significant space saving and increasedprecision can be obtained in all spray treatments including etching,outer layer formation, solder formation, basic processing, cleaning,rinsing and drying. High speed conveyors such as five feet per minuteconveyor speeds can easily be obtained with production of one hundredand fifty boards per hour in spray machines easily possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be better understood when read in conjunction with theattached drawings in which:

FIG. 1 is a semi-diagrammatic side view of a preferred printed circuitboard component conveyor in accordance with this invention;

FIG. 2 is a semi-diagrammatic cross-section thereof taken through line2--2;

FIG. 3 is a further semi-diagrammatic cross-section taken through line3--3 of FIG. 2; and

FIG. 4 is a semi-diagrammatic cross-section of a component thereof infragmented form taken through line 4--4 of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference now to the drawings, a printed circuit board conveyorapparatus is semi-diagrammatically illustrated in FIGS. 1 through 3, at10. The apparatus has a first horizontal path 11 from a starting pointor end 12 to a distant point 13 with an upper second path 14 returningtoward the starting point 12 and raised thereabove.

The apparatus 10 can have one or more treating stations along the firstpath 11. The treating stations can be one or more liquid spray means 15acting at one or more points along path 11. A plurality of spraytreatments such as washing and rinsing can be used with air knivesbetween each treating station as known in the industry.

In the apparatus 10, the conveyor drive means 20 extends along the firstand second path and carries a plurality of seriatim arranged frame means21 each having a hanger section 22 and a peripheral frame substantiallyplanar section 23 with a lower blade section 24.

The peripheral section 23 is in fact a frame. This frame is preferablymade of tubular material such as 3/16" diameter stainless steel roundwire of 304 stainless steel, titanium, polypropylene, polyvinylchlorideor the like. Round cross sections for the frame are preferred sinceminimized trapping of solution occurs with minimized surface area. Ofcourse the cross section, material and size of the frames can varygreatly depending on the components to be processed.

Each frame 23 is designed to hold a printed circuit board component 25with a plurality of such boards being shown in a plurality of seriatimarranged frames at FIG. 3. The boards are preferably surrounded by theframes although other arrangements are possible.

The components 25 can for example be plain copper sheet having a frontside and a rear side 26, 27 respectively and/or as is more often thecase in treating, thin copper sheets with substrates of resinimpregnated fiberglass or the like. Such components 25 are oftennon-rigid but self-supporting. They tend to wiggle when laidhorizontally. On the other hand, they can be mounted removably onconventional hanger pins such as wire spring pins 28 located at fourcorners of each frame to rigidify the board components and keep themsubstantially planar in a vertical plane when moving along the first andsecond path in the apparatus. The hanger pins 28 can have spacedV-shaped indentations 29 to maintain the boards against side-to-sidemovement within each frame 23. It is important that the frames be heldsubstantially rigid in the frame, but without stretch or distortion, toallow the force of spray means to apply substantially uniform liquids atall points along the surfaces on either side of the board component. Theparticular mounting pins and frame shapes can vary.

Because of the desirability of uniformity of spray, it is important thatthe frame itself be maintained substantially vertical and preferablysway no more that about one inch from side to side as it moves along thetrack. This is accomplished by means of a conveyor guide means 30 havingguide rails 31 and 32 within which a lower blade section 24 of eachframe is mounted. Thus as frames move along the first path in thedirection of arrow 40, they are maintained in substantially verticalalignment by the hanger section 21 and the frame blade sections 24. Theblade sections 24 maintain the frames in vertical position even as theyrise at the distant point 13 to the upper path at the second level as at14.

Below the conveyor guide means 30, formed by the rails 31 and 32, is afunnel trough 41 below which a catch basin can be positioned along thelength of the first path to catch fluids from the spray heads. Trough 41can be eliminated if desired.

The liquid spray means 15 as known in the art can be banks of sprayheads such as 43 to provide a uniform spray of solution to the printedcircuit board components 25. Preferably both sides are sprayed in normalprocessing as in cleaning. It is important that the positioning remainconstant from the spray heads to the board. The guide rail means andhanger means act in conjunction to provide proper distancing betweenboards and between the boards and spray heads.

As will be understood, although only one spray section is shown in FIG.2, spray treating stations can be positioned before the section of FIG.2 along the first path with a plurality of different spraying solutionsused if desired. Air spray knife blade mechanisms can be used toseparate one section from another by air sprays.

The conveyor drive means 20 can be a link belt or other conventionalendless conveyor drive for mounting the frames, as diagrammaticallyshown at 50, and moving them along the first and second paths shown atarrows 40 and 51. The drive means is mounted on a standard frame 52formed of I-beams, with upper and lower supports of steel 53, 55, 56 andend capstans such as 54 (only one shown). Each treating station ispreferably surrounded by a casing section of panels as indicated broadlyat 60 in the second path and 61 in the first path. A drip shield 63 ismounted on the hanger section above each frame means so that as theframe means move along the path and are carried upwardly, liquidsdripping from the board are caught and conveyed to a desired location.This is particularly desirable in the upper level travel where drippingsmay tend to contaminate lower boards unless drip shields are provided.The drip shields can be interconnected with tanks or just remain asholding bins if desired. The drip shields can be planar sheets ofplastic or metal with raised lips on one or more sides.

Preferably the second path is used for dry operations such as dryingstations. Thus the problems of liquid treating in overhead paths areavoided.

Preferably each compartment such as 60, 61 has a sliding seal as by ahard rubber shoe 62 slipping between a sliding surface 63 allowing thehanger sections to travel along with the compartment 60, 61 beingstationary. The seal which minimizes fumes to the environment can be inthe form of a curtain or drape.

In a typical apparatus for developing printed circuit board componentsin a method in accordance with this invention, a printed circuit boardconveyor apparatus as for example shown at 10 in FIG. 1 is set up to actas a developer. The first horizontal path at ground level is preferablyabout nine feet from starting point 12 to distant point 13 and is brokeninto three modules comprising a first developer module, a second rinsemodule and a third rinse module being four feet, two feet six inches andtwo feet six inches respectively in horizontal length. These modules canactually be one elongated compartment. The modules are preferablyseparated by air knife means which comprise vertical pipes as forexample sixty inches tall carrying one-eighth inch holes mounted atforty-five degree angles to the plane of travel of the frames. The holescan be spaced from top to bottom to provide sufficient air blast toclear liquids from the frames as they move from one module to anotheralong the path 11 from the point 12 to 13 and back toward the startingpoint 12 on the upper run.

In each module, there is a series of spray heads such as 43 comprisingin each module seven heads vertically arranged at approximately six-inchspaces with five rows to provide thirty-five nozzles on each side of theframe paths in each of the modules. Each of the nozzles can for examplehave a 6.9 inch cone circle of spray and are positioned six inches fromeach face of the board on either side thereof to deliver 0.89 grams perminute at twenty psi per nozzle.

In the developer module, printed circuit boards which may comprise forexample boards having dimensions of twenty-four inches by thirty-sixinches with the long side of the rectangle being positioned verticallyare each positioned and held in individual frames. The frames arevertically mounted as previously described with the copper boardscarrying a plastic pattern thereon when they enter the developer modulefirst in line in the pathway 14. The soft plastic of the pattern isremoved by the developer which can be a spray of sodium carbonateadmixed with butyl carbitol as known in the printed circuit industry.The two rinse steps are carried out in the two remaining modules whichhave spray head arrangements for spraying pure water (tap water in mostlocalities) to clear the developer are used. The upper drying chambercan be a conventional drying chamber with a steam core and fan to move140° to 160° F. heat from the core passed to both faces of the printedcircuit boards at approximately 110° F. When the boards are movedthrough the apparatus at a rate of 1.2 feet per minute the apparatus caneasily carry out developing and rinsing of thirty-two panels per hour.

The panels after the developing step in the apparatus 10 can be furtherprocessed in another apparatus such as 10, to carry out an etching stepto reduce the copper surface. Further conventional processing such asstripping of the resist can be carried out later. The apparatus of thisinvention can have the spray heads set up to carry out other steps thandeveloping as for example etching or resist removal and the like.

While a specific apparatus has been described, many variations arepossible. The number of spray stations can vary. In certain cases otherdrying and treating stations can be used on the upper and lower path inaddition to spray and drying stations. The particular frame means canvary although in all cases the frame is substantially vertically heldand preferably aligned with the planes of each board component treatedpreferably substantially traveling in a single plane. In some cases, theplane of each board may be somewhat at an angle to the path of travelalthough planar movement of the board as described is preferred toenhance ease of uniform application of spray fluids to the boards. Bladetype positioning means are preferred for sliding contact to keep theboards aligned while preventing the board components from moving out ofthe path of travel by any substantial degree. The frame means preferablysubstantially rigidify the board components. The particular developersolution used can vary as known in the art. Etchants used can besulfuric acid, cupric chloride or other known etchants. The resiststripping fluids can be as known in the art. The particular spray headarrangement as well as flow, times, and sizes of material can also varygreatly as known in the art. Speed of production can vary with theconveyor size, guide rail construction and distances to be traveled.While non-rigid boards are preferably treated with the spray means sincesuch non-rigid boards are customarily used in the printed circuit art,in some cases the boards are substantially rigidified and finalprocessing steps carried out on rigid boards.

What is claimed is:
 1. A printed circuit board conveyor apparatuscomprising a spray treatment line for moving a substantially planarcircuit board component having first and second sides along a first pathfrom a starting point to a distant point,said apparatus comprising aframe means for mounting said circuit board component for movement awayfrom said starting point along said first path to said distant point,said frame means extending so as to support each said component in asubstantially vertical plane with a component being mounted on eachframe means and each frame means comprising a blade means for engaging aguide rail in sliding contact therewith to maintain movement of saidframe in a plane, liquid spray means positioned on either side of saidpath for uniformly spraying said circuit board sides with liquid tocarry out a printed circuit processing step, conveyor guide means forcontacting said frame means in supporting relationship therewith tomaintain a predetermined position of the frame and fixed position ofsaid circuit board mounted thereon to aid in uniform application ofliquids by said liquid spray means, and a conveyor drive means mountingsaid frame means for moving said circuit board in said first path.
 2. Aprinted circuit board conveyor apparatus in accordance with claim 1wherein said frame means each comprise a tubular frame lyingsubstantially in a plane,each frame means having releasable means formounting a rigid or non-rigid printed circuit board component memberthereon, each frame means further comprising outwardly extending blademeans for engaging a guide rail in sliding contact therewith formovement in said plane.
 3. A printed circuit board conveyor apparatus inaccordance with claim 2 wherein said frame means comprises a generallyrectangular frame having an extension portion adapted to be positionedbetween first and second guide rails and a hanger section opposite saidblade portion.
 4. A printed circuit board conveyor apparatus inaccordance with claim 3 and further comprising a drip shield positionedon said frame means for preventing downward flow of fluids from saidframe means.
 5. In an apparatus for conveying a plurality of printedcircuit boards along a first path at a first level, the improvementcomprising,a frame carrying a printed circuit board, said frame definingan outer support perimeter, a top hanger section and a lower bladesection with said board being substantially arranged in a plane, saidframe carrying means for supporting a planar printed circuit boardcomponent in releasable engagement therewith while being mounted toprevent movement of said board from a predetermined plane while exposedto a plurality of processing conditions.
 6. The improvement of claim 5and further comprising said frame having a round cross section.
 7. Theimprovement of claim 5 and further comprising a drip shield mounted atsaid top section for preventing dripping of liquids from said frame to adirectly underlying area.
 8. A frame for use in conveying a plurality ofprinted circuit boards vertically arranged along a path,said framedefining an outer support perimeter, a top hanger section and a lowerblade section with said board being substantially arranged in a plane,said frame carrying means for supporting a planar printed circuit boardcomponent in releasable engagement therewith while said board is mountedto prevent movement of the board from a predetermined plane whileexposed to a plurality of processing conditions, said lower bladesection being adapted to move along a straight line path in slidingengagement with a guide rail.